SWODY2
SPC AC 220503
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1203 AM CDT THU SEP 22 2011
VALID 231200Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
ON FRIDAY...A HIGH AMPLITUDE UPPER AIR PATTERN WILL EXIST OVER THE
CONUS AND FEATURE A DEEP LONG WAVE TROUGH FROM THE MIDWEST TO THE
GULF OF MEXICO...AND AN AMPLIFYING RIDGE AXIS ACROSS THE CONTINENTAL
DIVIDE. SYNOPTIC FRONTAL ZONE WITHIN THE ERN FLANK OF THE LARGE
MIDWEST TROUGH WILL LIE IN QUASI-STATIONARY FASHION TO THE WEST OF
THE APPALACHIAN CREST...FROM WRN PA SWD AND SWWD ACROSS THE DEEP
SOUTH. THE AIR MASS EAST OF THE FRONT AND ACROSS MUCH OF THE EAST
COAST WILL BE CHARACTERIZED BY HIGH PW AND RICH BOUNDARY LAYER
MOISTURE SUSTAINED BY WEAK BUT PERSISTENT LOW LEVEL SLY FLOW OFF THE
WARM GULF AND ATLANTIC COASTAL WATERS. A WEAK SURFACE TROUGH AXIS
WILL BE SITUATED AMIDST THIS TROPICAL AIR MASS...FROM THE SOUTHEAST
TO THE MID ATLANTIC COASTAL PLAIN. EPISODIC SHOWERS AND TSTMS...SOME
POTENTIALLY HEAVY...ARE LIKELY TO PLAGUE AREAS FROM THE SOUTHEAST
AND MID ATLANTIC TO NEW ENGLAND AS DISTURBANCES ROTATE THROUGH THE
ERN FLANK OF LARGER SCALE UPPER TROUGH AND AID DEEP-LAYER ASCENT
ACROSS THE ERN SEABOARD.
...CAROLINAS TO DELMARVA...
IT IS TOO EARLY TO INTRODUCE EVEN LOW-END SEVERE WEATHER
PROBABILITIES OVER THESE AREAS GIVEN THE GREAT AMOUNT OF UNCERTAINTY
ABOUT AIR MASS DESTABILIZATION AND THE EVOLUTION OF POSSIBLE
MESOSCALE FEATURES THAT COULD SUPPORT MORE ORGANIZED STORMS.
SEVERE/ISOLATED TORNADO POTENTIAL WILL DEPEND ON THE DEVELOPMENT OF
SEVERAL INFLUENCES THAT ARE ONLY MARGINALLY SUPPORTED IN LATEST
GUIDANCE. THERE IS RELATIVELY HIGH CONFIDENCE THAT A VERY MOIST BUT
GENERALLY LOW-CAPE AIR MASS WILL BE SITUATED ACROSS THE MID-ATLANTIC
REGION. IF POCKETS OF GREATER SURFACE-HEATING CAN DEVELOP...LOCALLY
GREATER DESTABILIZATION MAY BE REALIZED. FURTHERMORE...THERE ARE A
WIDE RANGE OF POSSIBLE SURFACE DEVELOPMENT SCENARIOS BEING DEPICTED
IN LATEST GUIDANCE. IT SEEMS REASONABLE TO EXPECT WEAK SURFACE WAVE
DEVELOPMENT ALONG THE COASTAL PLAIN...OR PERHAPS ALONG THE IMMEDIATE
COAST...BY LATE FRIDAY NIGHT THROUGH EARLY SATURDAY. ANY SUCH
DEVELOPMENT COULD LOCALLY ENHANCE LOW LEVEL SHEAR AND...IN THE
PRESENCE OF STRONGER CONVECTION...SUPPORT THE CHANCE FOR AN ISOLATED
TORNADO EVENT. HOWEVER...DEGREE OF UNCERTAINTY SUGGESTS IT WOULD BE
PRUDENT TO REFRAIN FROM OVER FORECASTING THIS LOW-POTENTIAL SCENARIO
AT THIS TIME.
..CARBIN.. 09/22/2011
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